This invention relates to a fastener for clamping two panels together or for securing a panel to a body member between a flange-like head and a leg section of a female member with the leg section thereof spread radially outwardly by inserting a male member into the female member. More particularly, the invention relates to a fastener in which the female member is temporarily mounted within a hole of a first panel-like member, a second panel-like member is fixedly secured after inserting the male member into the female member, and the second panel-like member can be released by inserting the male member into the female member still further.